The traditional crypt(3C) Unix password encryption (= what the makekey command does) is technically known as a type of "salted hash".
The "salt" is a value used to modify the encryption process, to make it harder to reverse. The salt should usually be chosen randomly when the password is encrypted for storage.
The crypt(3C) algorithm takes a maximum of 8 characters as a password + 2 characters of salt.
So in your example, the password will be "ABcd@123", the salt will be "46" and the extra "6" at the end will simply be ignored.
(You could have replaced the "66" in your example with just "6" and still would have got the same result. The makekey command wants exactly 10 characters: if it gets less than that, it will fail. If it gets more than that, it gets the first 10 and ignores the rest.)
For each different salt value, the password will be encrypted in a different way. So it will be hard to confirm if someone else has the same password as you by simply comparing the encrypted passwords: if that other person has a different salt value, then the encryption result will be totally different, even if the actual password is the same.
Since the crypt(3C)-style password encryption is not effectively reversible, the password cannot be decrypted for checking. Instead, when the user enters his/her password into the password prompt at login, the user-entered password will also be encrypted, and then the encryption result will be compared with the stored encrypted password. But to make this comparision valid, the user-entered password must be encrypted using the same salt value as the stored password.
To make this possible, the salt must be stored unencrypted: it will be the first two characters in the encrypted password field.
I don't have a HP-UX system available at the moment, so I don't have the "makekey" command. But modern versions of OpenSSL also have a password encryption function, which handles several well-known password algorithms, including crypt(3C):
$ openssl passwd -crypt -salt 46 ABcd@123
46Qtr3Dtgy0u6
I think this is exactly the same as the value you got from the "makekey" command in your example, right?
As you can see, the salt appears unencrypted at the beginning of the encrypted result. This command makes it more obvious, as the salt must be entered using a separate option.
If the -salt option is not used, the "openssl passwd" command will choose the salt value randomly, so the encryption result will be different each time:
$ openssl passwd -crypt ABcd@123
S3oA559In3qHE
$ openssl passwd -crypt ABcd@123
4e.6PnvMJGuHo
$ openssl passwd -crypt ABcd@123
7S/umCxP4JdhM
MK
